Steel mills incorporate different types of furnaces. Slab reheating furnaces, annealing furnaces and other type of furnaces are typical in steel mill plants. The furnaces in general have a relatively low efficiency and an important portion of the heat produced as a result of the combustion of gas or other means, can't be transferred to the steel and is finally dissipated into the atmosphere.
Steel mills are major consumers of electrical energy. Most of the power plants in the world use fossil fuels that generate CO2 emissions. Therefore, it is important to reduce the electrical energy consumption to minimize CO2 emissions.
In some furnaces, a recuperator is included in the stack in order to heat the combustion air for the fuel or gas that is used to produce the heat required by the process. In other cases, the heat is used to heat water that is later used to heat buildings. A schematic diagram of a typical such system known in the art is presented in FIG. 1 in which primary exhaust gases 5 from furnace 10 are fed into a recuperator 15 through which incoming air or liquids 20 are cycled so as to transfer and capture heat energy in output air or liquids 25. The remaining secondary exhaust gases 30 are disposed of through stack 35. Even though these systems normally recover a significant amount of heat, some significant portion of the heat is still wasted by releasing hot gases to the atmosphere. The temperature of these exhaust gases remain high enough to warrant efforts to transform that heat energy into electrical energy.